From 76d3160cfabe15568f006ad530c105b9ad6fdcdd Mon Sep 17 00:00:00 2001
From: Rob Landley <rob@landley.net>
Date: Sat, 23 Jan 2021 03:00:35 -0600
Subject: Fix grep bug where -f /dev/null added "" regex matching everything,
 and address TODO where -z was still splitting patterns on \n

---
 tests/grep.test   |  6 ++++--
 toys/posix/grep.c | 26 +++++++++++++++-----------
 2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/tests/grep.test b/tests/grep.test
index e3753c2c..c6171112 100755
--- a/tests/grep.test
+++ b/tests/grep.test
@@ -85,7 +85,7 @@ testing "-r dir" "grep -r one sub | sort" "sub/one:one\nsub/two:one\n" \
   "" ""
 rm -rf sub
 
-# -x exact match trumps -F's "empty string matches whole line" behavior
+# -x exact match overrides -F's "empty string matches whole line" behavior
 testing "-Fx ''" "grep -Fx '' input" "" "one one one\n" ""
 testing "-F ''" "grep -F '' input" "one one one\n" "one one one\n" ""
 testing "-F -e blah -e ''" "grep -F -e blah -e '' input" "one one one\n" \
@@ -138,7 +138,7 @@ testing '' "grep -o -e '' -e two" "two\ntwo\n" "" \
   "one two three\none two\none\n"
 
 echo "one\ntwo\nthree" > test
-testing "-l trumps -C" "grep -l -C1 two test input" "test\ninput\n" \
+testing "-l overrides -C" "grep -l -C1 two test input" "test\ninput\n" \
   "three\ntwo\none\n" ""
 rm test
 
@@ -197,3 +197,5 @@ testing "-Fx" "grep -Fx h input" "h\n" \
   "missing\nH\nthis is hello\nthis is world\nh\nmissing" ""
 testing "-Fix" "grep -Fix h input" "H\nh\n" \
   "missing\nH\nthis is HELLO\nthis is WORLD\nh\nmissing" ""
+testing "-f /dev/null" "grep -f /dev/null" "" "" "hello\n"
+testing "-z with \n in pattern" "grep -f input" "hi\nthere\n" "i\nt" "hi\nthere"
diff --git a/toys/posix/grep.c b/toys/posix/grep.c
index fce8d564..2ddb6b93 100644
--- a/toys/posix/grep.c
+++ b/toys/posix/grep.c
@@ -372,13 +372,24 @@ static void parse_regex(void)
   // exit to free. Not supporting nofork for this command any time soon.)
   al = TT.f ? TT.f : TT.e;
   while (al) {
-    if (TT.f) s = ss = xreadfile(al->arg, 0, 0);
-    else s = ss = al->arg;
+    if (TT.f) {
+      if (!*(s = ss = xreadfile(al->arg, 0, 0))) {
+        free(ss);
+        s = 0;
+      }
+    } else s = ss = al->arg;
+
+    // Advance, when we run out of -f switch to -e.
+    al = al->next;
+    if (!al && TT.f) {
+      TT.f = 0;
+      al = TT.e;
+    }
+    if (!s) continue;
 
     // Split lines at \n, add individual lines to new list.
     do {
-// TODO: NUL terminated input shouldn't split -e at \n
-      ss = strchr(s, '\n');
+      ss = FLAG(z) ? 0 : strchr(s, '\n');
       if (ss) *(ss++) = 0;
       new = xmalloc(sizeof(struct arg_list));
       new->next = list;
@@ -386,13 +397,6 @@ static void parse_regex(void)
       list = new;
       s = ss;
     } while (ss && *s);
-
-    // Advance, when we run out of -f switch to -e.
-    al = al->next;
-    if (!al && TT.f) {
-      TT.f = 0;
-      al = TT.e;
-    }
   }
   TT.e = list;
 
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